Current motor vehicles comprise, in ever more sophisticated practical implementations, various means that warn the driver of events linked or related to the driving of the vehicle, for example, but in a non-limiting manner, of a permitted speed limit being exceeded, of an overspeed in the rotational speed of the motor in a given ratio of the gearbox, of the detection of the presence of another vehicle at the blind spot angle of the driver at the moment when his vehicle pulls out to overtake another car travelling in front of it or to pass some obstacle, of overstepping a continuous line of ground marking in the center of the roadway in some surface configurations, of a visibility limitation necessitating lighting the head lights of the vehicle, of a call on a hands-free car mobile telephone, or indeed of any other external reason whose sudden or gradual appearance requires an appropriate reaction from the driver.
It is in particular well known to generate, in response to an external event of this type, a vibratory alarm signal intended to warn the driver.
International patent application WO 2003/011638 discloses a vibrating warning device for a motor vehicle seat comprising an electric motor that is housed in a housing and that drives a rotation axle.
This axle has an extension that protrudes from the housing and on which a flyweight is mounted that consists of a heavy element fixed eccentrically on the axis so as to create an unbalance when the axis is driven in rotation by the motor.
Driving the unbalance in rotation brings about mechanical vibrations, the amplitude of which is a function of the driving speed of the axis of this motor.
The warning device is installed under the cover of the seat and is fixed to the cover via a flange that is held by screws so as to confine a metal thread of this seat cover between this flange and a flexible insert in contact with the housing of the motor.
Because of its positioning being somewhat spaced from the occupant of the seat, this type of device has to have a high vibrational power, leading to a rather high cost price and a significant increase in the total mass of the seat.
Moreover, because of its relatively large dimensions, it is at risk of being damaged by the occupant of the seat located behind the driver's seat if the occupant slides his feet below the seat.
To overcome these drawbacks, a vibrating warning device is known, in particular from US Pub. No. 2014/0008948, comprising a vibrating patch intended to be fixed by gluing to the padding of the seat or backrest of a motor vehicle seat.
This patch comprises a plurality of vibratory actuators of the LRA (linear resonant actuator) or ERM (eccentric rotating mass actuator) type interconnected in series or in parallel, these actuators being confined in a flexible support jacket formed by the two portions, which are folded onto themselves and glued together by a textile film.
To prevent, in particular, the patches mounted on the padding from detaching as a result of the repeated strains exerted on them when the occupant sits down and gets up from the seat, housings have to be specifically arranged in this padding to receive them, and this spaces them apart from the driver and reduces the vibration sensation performance.